The present invention relates to a drive device for a handheld heater unit for welding plastic sealing webs and sheets which is equipped with a heater device for heating the plastic sealing webs and sheets which are to be welded.
Handheld devices for welding plastic sealing webs and sheets are generally known and generally have an elongate housing for accommodating the control and drive units which are required. Depending on the design of the heater device heater units are divided into hot-air heater units and heating-wedge heater units and combinations thereof. In the hot-air heater units, air is heated and a specially designed welding tip is used to heat the material which is to be welded andxe2x80x94depending on the particular designxe2x80x94the tip. The air can be generated in the housing of the heater unit or externally. In the latter case, the air is supplied to the heater device arranged in the heater unit by means of a hose. In the case of the heating-wedge units, a heating wedge for welding the material is heated electrically. The application of pressure to the heated plastic webs is effected by means of a handheld roller which is to be guided by the user""s other hand.
Welding units of this type are used in particular when it is impossible to use automatic welding machines, which move forward automatically. This is the case when the weld seams are relatively short, the weld seam is not accessible on account of obstacles, such as for example walls, to an automatic welding machine on account of its width, when welding relatively long vertical or near-vertical surfaces or during overhead welding, in particular in tunnel construction.
To weld plastic sealing webs and sheets on vertical or near-vertical surfaces at maximum height of approx. 20 cm from the floor, it is possible for this to be carried out by means of a device described in CH 688 581 A5. This device has a chassis which has a drive device, and the chassis moves on the floor along the surface which is to be welded. The welding device is pressed by hand onto the vertical or inclined wall, in order to press together the plastic webs which have been heated by the heater device by means of a pressure-exerting roller which runs with it.
Therefore, the present invention is based on the object of proposing a possibility which allows a continuous welding process and an improved quality of weld when welding plastic sealing webs and sheets by means of handheld welding units.
According to the invention, this object is achieved by a drive device for a handheld heater unit for welding plastic sealing webs and sheets, which is equipped with a heater unit for heating plastic sealing webs and sheets which are to be welded, which drive device comprises an elongate housing with a pressure-exerting and driving roller arranged at the lower end thereof for applying a joining force to the plastic sealing webs and sheets in a vertical direction with respect thereto, a motor arranged in the housing for driving the pressure-exerting and driving roller, and a coupling unit for connecting the housing to the heater unit, such that longitudinal axes of the housing and the heater unit run substantially parallel to one another.
According to the invention, the drive device has an elongate housing which is designed to be sufficiently stable for it to be possible for the joining force required during welding to be applied to the plastic sealing webs and sheets in the vertical direction with respect thereto. The introduction of forces onto the materials is effected by means of a pressure-exerting and driving roller which is arranged at the lower end of the housing and is driven by means of a motor arranged in the housing. The drive device also has a coupling unit for connecting the housing to the heater unit. The coupling unit is designed in such a manner that the longitudinal axes of the housing of the drive device and of the heater unit run substantially parallel to one another. It is preferable for the height and/or distance of the pressure-exerting and driving roller with respect to the heater device to be adjustable. The pressure-exerting and driving roller may be arranged directly in the longitudinal axis of the housing or may be offset with respect thereto.
The substantially parallel arrangement of the drive device with respect to the handheld heater unit, which is usually also elongate, allows welding of plastic sealing webs and sheets to be carried out as close as possible to the edges and corners using this device even in the case of surfaces which are at right angles to one another. The minimum distance for the weld seam from a wall is determined by the diameter of the heater unit. The greater the inclination of the longitudinal axis of the housing and of the heater unit with respect to one another, the greater the distance between the wall and the seam which is still to be welded using this device becomes. The drive device has a single roller which forms both the pressure-exerting roller and the driving roller. The connection of the housing to the heater unit by the coupling unit means that the drive device is fixedly connected to the heater unit, and the joining force is applied to the plastic sealing webs and sheets in the vertical direction by pressing onto the housing of the drive device, after the plastic sealing webs and sheets have been heated appropriately by the heater unit in the region of the overlapping ends of the plastic sealing webs and sheets which are to be welded. In this way, the overall arrangement allows easier welding with improved quality on vertical walls or in tunnel construction.
Therefore, the drive device allows handheld welding with an improved welding quality and at a higher speed. The heater unit and the corresponding heater device, for example tip or heating wedge, are also moved continuously with the movement of the pressure-exerting and driving roller. The rotational speed of the pressure-exerting and driving roller can be adjusted variably according to the material; according to one design, there is a control device which keeps the rotational speed constant even when the pressure exerted by the operator drops. In this way, the process is optimized, since the operator only has to concentrate on applying the pressure, while the second welding parameter, namely speed, is regulated or controlled by the drive device, and the third parameter, namely temperature, is controlled or regulated by the heater unit (in a known and customary way).
The use of the drive device also provides a visual quality improvement, which makes its presence felt in particular, for example, in swimming pools, since compared to a weld seam which is produced using a handheld roller, the surface looks more even, and the stripes which are at an angle to the weld seam and which often occur during handheld rolling do not occur when the melt is rolled out.
It is preferable for there to be a guiding aid to the side of the pressure-exerting and driving roller, in order to reduce the tilting of the pressure-exerting and driving roller during the welding process. This can be effected, for example, by a supporting ring or an additional supporting roller. This ensures that, during the movement of the drive device, the largest possible pressure-exerting area acts on the material, and the user does not tilt the entire device excessively through the lever arm, which is relatively great on account of the structure, which would have an adverse effect on the quality of the weld seam.
In a further refinement, the pressure-exerting and driving roller is mounted in a swinging manner. This makes it possible to compensate for slight tilting by the operator when the joining force is being applied. In particular, a supporting aid is then no longer required. The swinging mounting may be produced, for example, using the bearing arrangement of the swinging roller described in EP949057A1. Another possibility is to form a swinging head in the longitudinal axis of the housing with corresponding angular gears for transmitting the driving force.
According to a further advantageous configuration, the angle between the pressure-exerting and driving roller and the overlapping edge is adjustable. During the therefore slightly inclined forward movement, the operator is forced to counteract this by the application of lateral pressure. Therefore, during the forward movement the material is pulled toward the overlap edge, and the formation of creases is avoided.
According to a particularly preferred embodiment, the pressure-exerting and driving roller is mounted resiliently, so that when the joining force is being applied the heater device can adjust to unevenness, and the load of the joining force is not applied to the heater device. The resilient mounting can be produced either by direct resilient mounting of the pressure-exerting and driving roller or by resilient mounting of the housing of the drive device, which is rigidly connected to the pressure-exerting and driving roller, with respect to the heater unit.